2008 Prius engine clicking sound - 91 Octane gas

I personally hold little hope for knock sensor fixing the noise in my car, I know its definitely fuel ping that im hearing its very common for "underpowered" cars to ping on load if using low grade fuels, my little combo van used to do the exact same! prius has a small engine with moderate size body then add a big hill and aging traction battery ...pingtingdingping... if its knock sensor every prius in my town must need a new one because they all do it, and petty much every prius in my town has high mileage and a sad old battery!

Im not saying you "need" a new battery but I will mention, I notice cars with a failed hv battery ping pretty darn bad because they have little or no electric assistance to help push the car up hills, once I install a new/reco hv battery the ping phenomena is reduced dramatically.

my 08 has about 3600mA In its weakest block of the hv

swprius08 ..no I havent done anything to fix it, I simply work around it by paying a few cents extra for quality fuel and adding injector cleaner occasionally (mainly because I have heaps of that stuff and its a slight octane boost) my 08 has done 483,500km I plan to keep changing oil every 10k and nursing it until it dies then I will just replace the car, almost half million k on a 4cyl, what a legend. go toyong.

 

Yes, 89-90 AKI is equivalent to RON 95. I hope you understand that the only thing different between RON, MON and AKI is the method at which the numbers are derived. The fuel tested is exactly the same, but using the different test methodologies, a different number is derived.

Wasn't specifically aware of that, but I imagine you have to go well above the recommended octane rating to have that effect.

Are they all using 95 RON? Perhaps that is part of the problem, if they are not.

That is your choice, personally if my car ran fine on 87, then I would use that. I note you have a Prius c, may be that has a different specification to the Gen II Prius discussed here. I can't imagine that the Gen II would have a different specification for the US, as the engine used, to the best of my knowledge, is exactly the same. I'd be interested if someone could post a picture of the relevant page from a Gen II manual.

Re the "or higher" bit, it is in the sense that if the grade specified is not available, then use a higher octane rating, not lower. Most people do not have a clue (as evidenced by the varied discussions I have seen on the subject) what octane rating is about, so it is spelled out for them.

He's what my manual says on the subject of fuel selection (page 212):


Note the cautions in regards to using lower octane rating and engine knocking.

In any case, persistent heavy knocking is not good for the engine and should be rectified as soon as possible.

 

Thanks for the tip, I understand the different test methods I just didn't realise the US states were going on the AKI system, see people on here throwing numbers around (87-91 etc) but hadn't noticed they were actually talking AKI rather than RON. I no longer buy 91 RON anyway the ping drives me pinging nuts, I always use either E10 (about 95 octane) or 98, sometimes regular 95 + injector cleaner but personally I wont use performance additives or cleaning agent additives along side 98 octane or E10 in fear of overheating the poor old thing.

& yes from memory you have to get up near 100 octane before heat causes any problems, easy enough to do in Australia when you incorporate extra u-beaut fuel additives along with 98 ron (or accidently pull up to the e85 pump lol) Personally never had the problem but a few "car guys" have advised me to be careful, probably an old-school problem these modern day engines perhaps don't even care.

Might try new spark plugs for a giggle, I don't know how old mine are.

I believe most cabs around here are instructed to buy 91 that might be why they rattle, every one of them.. bar none!

 

I dare say you are right, I know I didn't notice any pinging when I used 91 in mine. What I did notice was a more sluggish car that got worse fuel economy. I have also run 95 and 98 and didn't notice any benefit to using 98 (over 95), but benefit (peppier and better fuel economy) over using 91.

I suspect being instructed to use 91 might be to save money, as it is cheaper, but it is a false economy as you can't go as far per tank.

Anyway, all the best sorting out the pinging.

 

I mainly notice the ping getting better or worse, no noticeable difference in performance and its hard to say if economy is any better or worse because conditions aren't stable enough around here to conduct any real comparative testing.

The cabbie I was speaking with did say they used to run E10 but have since been asked to buy 91, bit strange because E10 is actually cheaper than 91 here. I didn't question their motive im a bit sick of the E10 vs conventional fuel debate, its a Prius not a Ferrari 6 of one half dozen the other.

Not even going to "sort it out" at 483k-k im happy to nurse it until it blows then just replace the car..

Cheers

 

I'd emphasise the two words light and short.

Out of interest, what does your manual say on the equivalent page?

 

Thanks for that SW, I find it interesting that the US specs 87 AKI (RON 91) for the Gen II.

I have run mine on 91, and while it doesn't cause any issues with pinking, it definitely drives better on RON 95 (91 AKI), as I mentioned in post #25.

Another factoid, even though there is about a 6-8c/litre premium to buy 95 over 91, it works out cheaper (for me) to use 95 as I get more kms (avg 100 km) per tank using 95. So it costs (on avg) 9c per km on 95 vs 9.6c per km on 91. These prices are worked out using the pump prices at the last fill on 7 Oct - 1.969/litre for 91 and 2.049/litre for 95. Prices are on the rise, unfortunately (2.079/litre for 95 now).

Here's a chart of NZ fuel pricing and equivalent US/UK/AU prices as at 7 Oct 2016:

[EDIT] Added Oz pricing.

 

was driving a low-ish mileage (160,000km) 2005 today, I floored it up hill with batt at 60% and it was pinging

less pining and noticeable power increase compared to my tired 08 ..

not sure what fuel it was running though

I think they all do it, if you load them up enough on a good enough hill

 

I think you're right, most if not all do it on hills and such. I've never heard a 1.8 Prius do it though

 

The thing is, we all have different fuels by regulations. It possibly makes sense for the New Zealander to see better MPG on Premium as he does not have U.S.A./Ca. reformulated gasoline, which basically takes the more energetic components out for the purpose of reducing emissions. So if you read Chevron website info they say in some areas Premium could have a little more energy, but not expected in reformulated gasoline zones (Ca.).

Now then in the case of a malfunctioning older Prius with some type of carbon build-up/knocking problem, I suppose it's possible Premium could be better MPG in Ca. That's an exception case over my pay grade.